I doubt Dexter's the psychopath Vogel thinks him to be, he's
shown clear signs of humanity in his refusal to kill Doakes, who
was a clear threat to him, but was innocent, nonetheless. According
to the 'Don't get caught' rule of the code, Doakes met the
requirements for a kill, yet Dexter didn't go through with it. As
far as Vogel's claim of him showing love, care or affection for
purely selfish reasons, that's clearly not true, since he took care
of Lumen and freed her selflessly, even though she just saw him
murder a man and was a clear threat. I think all that will probably
be made more clear as the series comes to a final close.